Compaction machines or devices of the respective kind are used for compacting soil, grounds, traffic routes, dams and the like. Such compaction machines are known in different embodiments from the state of the art. These can concern for example, but not exclusively, automotive rollers or towed rollers. The invention must be distinguished from apparatuses (such as rams or beetle heads) for driving land ties and the like into the ground.
In order to improve the compaction effect and for increasing the degree of compaction, a vibration superimposition or oscillation excitation of the compaction tools is known, for which reference is made in lieu to DE 33 08 476 A1. The respective compaction machine is then provided with a vibration plate or roller, as described in WO 02/25015 A1.
A relevant problem in this respect is that the compaction machine per se as well as structures in the surrounding area can be damaged by the oscillations. This is especially problematic in cases where the frequency of the oscillation excitation lies in the range of the local natural frequency of the machine or the ground, or when large oscillation amplitudes are applied. It is therefore known from the state of the art to detect the oscillations and to correct them optionally via a control circuit in order to also prevent any undesirable “jumping” of the machine. Such a feedback control is described in EP 0 688 379 B1 and the already mentioned WO 02/25015 A1. The compaction machine or the compaction tool is equipped with sensors for detecting the oscillations. The oscillations in the ground per se or the surrounding structures are not considered.
It is the object of the invention to provide a method for controlling a compaction machine and a respective system with which the same can be operated with high efficiency concerning the compaction effect and the degree of compaction, and with which adjacent structures are not stressed more than permitted by vibrations at the same time.
This object is achieved by a method according to claim 1 and by a system according to the independent claim. Advantageous further developments are the subject matter of the respective dependent claims.
The method in accordance with the invention provides that the oscillations emitted by the compaction machine and propagating the ground are detected in at least one relevant measuring location by means of at least one sensor and the measured oscillation values as detected by the sensor are sent to at least one data-processing unit (9) which compares these with a permissible oscillation limit value for the respective measuring location. When the permissible limit value for the respective measuring location is exceeded, it is provided to change at least one compaction parameter automatically, i.e. in a control circuit, with the objective to set the oscillation values measured at the measuring location to a value smaller than or equal to the oscillation limit value, or to influence the compaction parameter in such a way that the maximum detected measured oscillation value is smaller than or equal to the oscillation limit value.
Compaction parameters shall be understood within the terms of the patent application as being a physically detectable variable which has influence on the compaction effect or the degree of compaction. The compaction parameter is preferably taken from a group which comprises the oscillation amplitude of the compaction tool, the direction of action of said amplitude, the different directional portions of said oscillation, the frequency of the oscillation or also the speed of displacement or mass of the compaction machine.
A relevant advantage of the method in accordance with the invention is that the measurement occurs directly on the relevant or interesting measuring location, i.e. usually directly in a structure. Local and momentary properties of the ground thus have no influence on the measured oscillation values as detected in the structure. An imprecise determination of load on the basis of any inverse calculation or projection with ground parameters (such as oscillation propagation velocity and damping) which cannot be specified more closely can be omitted.
This means that the compaction machine can be operated with very high efficiency concerning compaction effect and degree of compaction. At the same time, the surrounding structures and especially those susceptible to oscillations can be protected in the best possible way against vibrations, such that they are subjected to oscillations to an extent not more than is permissible.
The system in accordance with the invention comprises at least one sensor for detecting an oscillation caused by and emitted from the compaction machine and at least one data-processing unit which compares the measured oscillation values sent by the at least one sensor with a permissible oscillation limit value. When the limit value is exceeded, the data-processing unit initiates the change of at least one compaction parameter of the compaction machine. The at least one sensor is arranged in the area of a structure in the ground or on the structure itself in order to directly detect the oscillations occurring at the measuring location.
Reference is hereby made substantially to the discussion above in connection with the control method concerning the advantages of such a system.
In an especially preferred further development of the invention, for which protection is hereby filed optionally, it is provided that several compaction machines are operated at a construction site. The position of each compaction machine is detected absolutely or at least relatively with respect to the position of the sensors. Furthermore, a data-processing unit is associated with each individual compaction machine which analyzes the measured oscillation data of all sensors and calculates on the basis of the known position of the compaction machine which sensors and which measuring locations are relevant for the respective compaction machine and which are not. In the event that a measured oscillation value exceeds the permissible limit value at a measuring location relevant for the compaction machine, the data-processing unit will initiate a respective change of at least one compaction parameter with the respective compaction machine. An especially advantageous further development provides that all compaction machines are controlled by only one central data-processing unit, with each machine being provided itself with a data-processing unit, especially when the positional data are evaluated which are received by a navigation system such as GPS.
Several embodiments of the invention and their advantages are described below by reference to the drawings. Features which are only shown in connection with one embodiment shall also apply as general features of the invention, within the scope of what is technically feasible.